1. Field of the Invention
The present invention relates to a mobile telecommunications system and, more particularly, to a route guidance system applicable to a mobile telecommunications system for guiding an automotive vehicle or similar vehicle along a particular route to a destination.
2. Description of the Prior Art
Typical of the route guidance system for a mobile telecommunications system with which the present invention is concerned is a navigation system for automotive vehicles. In an automotive vehicle navigation system, an on-board unit mounted on a vehicle has a CD-ROM or similar optical storing medium which is loaded with stored map data and a CRT or similar display capable of displaying the map data thereon. With this system, it is possible to indicate the instantaneous position of the vehicle on a map being shown on the display. The navigation system is implemented by a transmitter mounted on a roadside sign plate, for example, and a receiver mounted on a vehicle, the transmitter transmitting position data representative of the transmitter to the receiver. Every time the receiver receives position data from such a transmitter, the instantaneous position of the vehicle appearing on the display is updated. During the interval between the reception of position data from one transmitter and the reception of position data from the next transmitter, the position of the on-board unit is updated automatically as determined on the basis of the travelling direction and travelling velocity of the vehicle. The occupant of the vehicle is allowed to recognize the varying position of the vehicle by observing the position in the map being indicated on the display and to thereby determine whether or not the vehicle is following the right way to the destination.
The prior art navigation system stated above has various drawbacks left unsolved, as follows. The occupant has to select an adequate route to the destination by the own discretion, i.e., all that can be seen is whether or not the vehicle is travelling the right way to a destination. The occupant, of course, cannot select an optimum route matching the instantaneous traffic conditions because the occupant determines the route to a destination by mere conjecture. When the instantaneous traffic conditions are changed due to an accident or similar cause, the occupant of the vehicle cannot cope with it immediately and, in the worst case, only particular roads will congest with a number of vehicles. Further, each vehicle has to be furnished with map data. It is extremely difficult to furnish a vehicle with minute map data which cover all the possible areas of interest due to, among others, the limited capacity of the previously mentioned storing medium. This practically inhibits the occupant from selecting an adequate route, depending on the destination. Map data in itself is sequentially updated with time and is sometimes temporarily changed in association with the unusual occurrences such as traffic accidents and road constructions. Hence, even if such variable data are prepared beforehand, it is almost impracticable to deal with the change or the addition of data rapidly.